com.jdroid.java.json.JSONWriter Maven / Gradle / Ivy
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package com.jdroid.java.json;
import java.io.IOException;
import java.io.Writer;
/*
* Copyright (c) 2006 JSON.org Permission is hereby granted, free of charge, to any person obtaining a copy of this
* software and associated documentation files (the "Software"), to deal in the Software without restriction, including
* without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the
* Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions: The
* above copyright notice and this permission notice shall be included in all copies or substantial portions of the
* Software. The Software shall be used for Good, not Evil. THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY
* KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR
* PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR
* OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
* SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
*/
/**
* JSONWriter provides a quick and convenient way of producing JSON text. The texts produced strictly conform to JSON
* syntax rules. No whitespace is added, so the results are ready for transmission or storage. Each instance of
* JSONWriter can produce one JSON text.
*
* A JSONWriter instance provides a value method for appending values to the text, and a key
* method for adding keys before values in objects. There are array and endArray methods that
* make and bound array values, and object and endObject methods which make and bound object
* values. All of these methods return the JSONWriter instance, permitting a cascade style. For example,
*
*
* new JSONWriter(myWriter).object().key("JSON").value("Hello, World!").endObject();
*
*
* which writes
*
*
* {"JSON":"Hello, World!"}
*
*
* The first method called must be array or object. There are no methods for adding commas or
* colons. JSONWriter adds them for you. Objects and arrays can be nested up to 20 levels deep.
*
* This can sometimes be easier than using a JSONObject to build a string.
*
* @author JSON.org
* @version 2011-11-24
*/
public class JSONWriter {
private static final int maxdepth = 200;
/**
* The comma flag determines if a comma should be output before the next value.
*/
private boolean comma;
/**
* The current mode. Values: 'a' (array), 'd' (done), 'i' (initial), 'k' (key), 'o' (object).
*/
protected char mode;
/**
* The object/array stack.
*/
private final JSONObject stack[];
/**
* The stack top index. A value of 0 indicates that the stack is empty.
*/
private int top;
/**
* The writer that will receive the output.
*/
protected Writer writer;
/**
* Make a fresh JSONWriter. It can be used to build one JSON text.
*
* @param w
*/
public JSONWriter(Writer w) {
comma = false;
mode = 'i';
stack = new JSONObject[maxdepth];
top = 0;
writer = w;
}
/**
* Append a value.
*
* @param string A string value.
* @return this
* @throws JSONException If the value is out of sequence.
*/
private JSONWriter append(String string) throws JSONException {
if (string == null) {
throw new JSONException("Null pointer");
}
if ((mode == 'o') || (mode == 'a')) {
try {
if (comma && (mode == 'a')) {
writer.write(',');
}
writer.write(string);
} catch (IOException e) {
throw new JSONException(e);
}
if (mode == 'o') {
mode = 'k';
}
comma = true;
return this;
}
throw new JSONException("Value out of sequence.");
}
/**
* Begin appending a new array. All values until the balancing endArray will be appended to this array.
* The endArray method must be called to mark the array's end.
*
* @return this
* @throws JSONException If the nesting is too deep, or if the object is started in the wrong place (for example as
* a key or after the end of the outermost array or object).
*/
public JSONWriter array() throws JSONException {
if ((mode == 'i') || (mode == 'o') || (mode == 'a')) {
this.push(null);
this.append("[");
comma = false;
return this;
}
throw new JSONException("Misplaced array.");
}
/**
* End something.
*
* @param mode Mode
* @param c Closing character
* @return this
* @throws JSONException If unbalanced.
*/
private JSONWriter end(char mode, char c) throws JSONException {
if (this.mode != mode) {
throw new JSONException(mode == 'a' ? "Misplaced endArray." : "Misplaced endObject.");
}
this.pop(mode);
try {
writer.write(c);
} catch (IOException e) {
throw new JSONException(e);
}
comma = true;
return this;
}
/**
* End an array. This method most be called to balance calls to array.
*
* @return this
* @throws JSONException If incorrectly nested.
*/
public JSONWriter endArray() throws JSONException {
return this.end('a', ']');
}
/**
* End an object. This method most be called to balance calls to object.
*
* @return this
* @throws JSONException If incorrectly nested.
*/
public JSONWriter endObject() throws JSONException {
return this.end('k', '}');
}
/**
* Append a key. The key will be associated with the next value. In an object, every value must be preceded by a
* key.
*
* @param string A key string.
* @return this
* @throws JSONException If the key is out of place. For example, keys do not belong in arrays or if the key is
* null.
*/
public JSONWriter key(String string) throws JSONException {
if (string == null) {
throw new JSONException("Null key.");
}
if (mode == 'k') {
try {
stack[top - 1].putOnce(string, Boolean.TRUE);
if (comma) {
writer.write(',');
}
writer.write(JSONObject.quote(string));
writer.write(':');
comma = false;
mode = 'o';
return this;
} catch (IOException e) {
throw new JSONException(e);
}
}
throw new JSONException("Misplaced key.");
}
/**
* Begin appending a new object. All keys and values until the balancing endObject will be appended to
* this object. The endObject method must be called to mark the object's end.
*
* @return this
* @throws JSONException If the nesting is too deep, or if the object is started in the wrong place (for example as
* a key or after the end of the outermost array or object).
*/
public JSONWriter object() throws JSONException {
if (mode == 'i') {
mode = 'o';
}
if ((mode == 'o') || (mode == 'a')) {
this.append("{");
this.push(new JSONObject());
comma = false;
return this;
}
throw new JSONException("Misplaced object.");
}
/**
* Pop an array or object scope.
*
* @param c The scope to close.
* @throws JSONException If nesting is wrong.
*/
private void pop(char c) throws JSONException {
if (top <= 0) {
throw new JSONException("Nesting error.");
}
char m = stack[top - 1] == null ? 'a' : 'k';
if (m != c) {
throw new JSONException("Nesting error.");
}
top -= 1;
mode = top == 0 ? 'd' : stack[top - 1] == null ? 'a' : 'k';
}
/**
* Push an array or object scope.
*
* @throws JSONException If nesting is too deep.
*/
private void push(JSONObject jo) throws JSONException {
if (top >= maxdepth) {
throw new JSONException("Nesting too deep.");
}
stack[top] = jo;
mode = jo == null ? 'a' : 'k';
top += 1;
}
/**
* Append either the value true or the value false.
*
* @param b A boolean.
* @return this
* @throws JSONException
*/
public JSONWriter value(boolean b) throws JSONException {
return this.append(b ? "true" : "false");
}
/**
* Append a double value.
*
* @param d A double.
* @return this
* @throws JSONException If the number is not finite.
*/
public JSONWriter value(double d) throws JSONException {
return this.value(Double.valueOf(d));
}
/**
* Append a long value.
*
* @param l A long.
* @return this
* @throws JSONException
*/
public JSONWriter value(long l) throws JSONException {
return this.append(Long.toString(l));
}
/**
* Append an object value.
*
* @param object The object to append. It can be null, or a Boolean, Number, String, JSONObject, or JSONArray, or an
* object that implements JSONString.
* @return this
* @throws JSONException If the value is out of sequence.
*/
public JSONWriter value(Object object) throws JSONException {
return this.append(JSONObject.valueToString(object));
}
}